Telegraph distributor



5 Sheets-Sheet l G. T. DAlN TELEGRAPH DISTRIBUTOR Sept Filed June 10, 1949 u QI 5 Sheets-Sheet 2 G. T. DAIN TELEGRAPH DISTRIBUTOR .Il Il ll sept. 3o, 1952 Filed Junev 10, 1949 M @ZM/ua, W'M

Sept. 30, 1952 G, T, DAlN 2,612,563

TELEGRAPH DISTRIBUTOR Filed June l0, 1949 5 Sheets-Sheet 5 o zo 40 6o 8o /oo /20 /40 /60 /60 am @L www 5 Sheets-Sheet 4 L lzl.

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G. T. DAlN TELEGRAPH DISTRIBUTOR Sept. 30, 1952 Filed June 10, 1949 Till 5 Sheets-Sheet 5 G. T. DAIN TELEGRAPH DISTRIBUTOR -1 zls sept.v 3o, 1952 Filed Jne i0, 1949 Patented Sept. 30, y19.52

' lUlti/rs13 STATE TELEGRAPH DISTRIBUTOR Gordon Taylor Dain, Buckinghamshire, England,

assgnor to British Telecommunications Research Limited, `Taplow,

Buckinghamshire,

r England, a British company Application June 10, 1949, Serial No. 98,221 In Great Britain June 14, 1948 15 Claims.

' The presentinvention relates to distributors used in telegraph systems for the purpose of controlling the successive elements which form the coded representation of a character.

Usually a set of potentials representing the ele-l mentsof a character in code are generated simultaneously and are rendered effective successively to control the transmission of a pulse train representative of the character. This operation is effected-by a distributor and a number of types t ofdistributor are known. involving mechanically moving parts.

, It is; the principal object of the present invention to provide a-distributor which does not dependvfor its operation on moving parts.

According to one feature of the invention a telegraph distributor comprises a combination of devicessuch as electronic switching means having no mechanically moving parts to which potentials representing a character in code are applied simultaneously, said devices being subsequently rendered elective successively and the eiective, impedance thereof is adapted to be controlled by said potentials to enable the transmission of signals corresponding to said potentials.

According toanother feature of the invention, a telegraph distributor comprises a transmitting device, a plurality of control circuits, means for simultaneously applying potentials representing a -character in code to said control circuits'and meanslflor enabling said control circuits to pass pulses successively and Ythereby to control the transmitting device to transmita pulse train as determined-by said -potentials.-k

c According to a further feature of theinvention, atelegraph distributor comprises a transmitting device, :aplurality of control circuits, means for applying simultaneously-to said control circuits a set of potentials representative of a character in code, a plurality of trigger circuits for rendering said control circuits effective successively to enable said control circuits'to pass pulses depending on the potentials applied'thereto and means for controlling said transmitting device in accordance with the pulses passingthrough said control circuits, l 'f 4The control circuits arerendered effective under the control of circuits which-,are triggered successively.- Each trigger circuit includes two crossconnected triode valves arranged to have at least onestable condition'of equilibrium and in one embodiment each control circuit includes a pentode vvalve while 'in-.another each control circuitl includes a dry plate rectifier.

- Further oneio'f thetrigger circuits is arranged to-operate` aathermionic valve circuit which controis the transmitting device-.to enable a start signal to be' transmitted=prior`f to the pulse train while a-ffurther thermionic circuit controlled by thelasttrigger circuit to be operated Serves t control' the application of another set fof `pof-`v tentials representing the next characternto be transmitted to the control circuits. The invention will be better understood-from"- vthe following description of two embodiments read in conjunction` with the accompanying drawings in which: v

Figs. l and 2 when placed side-by-side with Fig. l on the left show the complete circuit of one embodiment,

Fig. 3 shows the voltage-time curve developed on the control grid of the right-hand valve of Vt and e Figs. 4 and 5 when placed side-by-sidejwith Fig. 4 on the left show the complete circuit of a second embodiment. y

The invention is described with reference `to teleprinter transmission in which the characters, are represented in a five-unit code on a punched tape in the well known manner. A set of pecker contacts is providedin the transmitting auto-head and these are arranged to take upy a L in-a'rlscr. space position as determined by the presence or absence of a hole in the tape. The pecker contacts control the potential applied to the k appropriate ones of the leads l to 5 (Figs. 2 land 5),.

Referring to Figs. 1 and 2, valves Vl and lV9 and their associated circuits constitute the time base generator; valves lV2--V'I inclusive and their associated circuits are the trigger circuits; valves VI l-VI5 and their associated circuits form the control circuits andare individually associated with the trigger circuits; valve VID is provided for introducing a start signal; valve V8 land telegraph relay T constitute the transmitting de-v vice; and valve Vl 6 andhigh speed relay P control the stepping on of the` tape at the end vof the transmission of one character so that the next character may be transmitted without delay.

vThe time base generator'consists of a doubletriode valve VI used las a multivibrator.'v This type of circuit gives4 a relatively constantfrequency with a Wide range of applied voltage-:In the circuit shown the timev constants of theftwo grid circuits are unequal sovthat the'- multivibrator is asymmetric and the voltage-time curve at the control grid of the right-hand triode is similar to that shown in Fig. 3. The duration of a complete cycle is 150 milliseconds and the main sweep, as can be seen from Fig. 3 occupies ap-l proximately milliseconds of this time. vEach complete cycleA corresponds to one 'telegraph character.y Different speeds of transmission may be obtained by varying the frequency of'operaation of the time-base-generator. l

The output of valve VI is applied to the control and suppressor grids of a cathode follower Vpentode valve V9 connected as a triode. The voltage developed across the cathode resistor Rlfoff-:valve V9 is therefore similar to that shownin. Eig.3.

At thebeginning of each sweep: therr'ghtehand.

triode of all the trigger circuits is conducting. Since' the voltage from the cathode follower valve V9 is at its minimum, each of .theleft-handtriodes is suppressed due to the connection of nthe left-hand anode to the cathode resistor which is also common to the right-hand triodeof the same valve. These cathode resistors are adjustedfsuch that .as the sweep voltageincreases, the left-'hand triodesare triggered. vat 20 millisecond intervals from .thestart of. the sweep. The.

leftihanditriode ofthe last trigger-'*valvez-VI' conductslZO'milliseconds after the start of thesweep andlfrom this time until the-end of 'the sweep the left-hand triodes of all six' tr'iggercircuits areconducting.

At4 the endv of a sweep the sweep voltage is returned to its minimum value as shownin Fig. 3.- 'Since this' y back is of. negligible duration, all the left-hand triodes of valves V2-V'I inclusive are suppressed and the right-hand triodes conduct simultaneously.

Aseach left-hand triode of a trigger circuit conducts, a negative pulse is sent from its anode via `a-condenser such as CI to the control grid ol'ithe-'right-'hand triode. This negative pulse is sui'cient to cut off'the right-hand triode. The timeconstants of the grid-circuits of 'therighthandtriodes are such that the right-hand triodes-fremain cutoff until'the end of the sweep i'. e.theremainder of the duration ofthe character. y It Will be 'seen that at the instant4 when the left-'handtriode of any vtriggervalve conducts, two'lpu'lses are'ravailabyle, viz. a negative pulse from"the 'left-hand triodeanode and a positive pulse from the right-hand triode anode. These twopulsesare used tot control the operation of the control val-Ves. In the case of valve V'I the positive pulse is used 'to operatev the auto-head drive 'ci'rcuitas will lbe described later.

Valve V4.0/ and 'theyve control valves VIf-IV`I-5inclusive are all pentodes and are fed froma commonanode resistor RIA. The screen grid 'oi' eachvalve isV permanently connected to H; T. positive via a suitable resistor, and in the case offvalves VI IVI5 inclusive the screen grid is-falso l'connected tol thev auto-'head pecker contacts via'leads I, 2, 3, 4 and 5.

IConsiderthe condition oi' the circuit at the beginning of a sweep. The fly-back at the end offthe previous -sweep will cut off the left-hand f tri-odesrof all the trigger'circuits and in particular the-left-hand triode of` V2. This will cause a positive-going pulse to lbe transmitted from the left-hand anode via condenser C2 and RI5 to thecontrol grid of valve VIH. This therefore conductsfandaswm be described later causes af-space 'signal to be transmitted to line to form aA startv signal. After 20 milliseconds of the sweep; thelef-t-hand triode vof V2v conducts and therighthand triode is sup-pressed. The negative-goingr pulse from thefleftlhand anode is fed toft'h'e-control grido'f'VI which Vis thus cut' off while the positive-going pulse from the righthand 'anode is `fedvia C3v and RIB to the control grid'of =VII i..e. the-first control circuit is renderedc-eifectiver The time constantk of the control-grid. circuitsof VIO= .isf-such Athat .the valve remains suppressed at least untilth'e end of the sweep. If the pecker contacts associated with "lead I are in the spacing condition, lead I will bedisconnected and the screen voltage of VI I will be positive. Valve VII will thus conduct and a 'spacesignalwill beftransmitted to line as the first element of thecharacter. If however, the pecker contacts 'are in the marking condition, leadl I will? be-connected to earth and VII will not conduct.. yAniarking signal will thus be transmitted .to-line After a further 20 milliseconds i. e. 40 milliseconds Vafter the beginning of the sweep, V3 will be triggered by the sweep voltage and a negativeegoing pulsewill 'beafedi via' C4 vand 1R11 to thezisuppressor 'grid ofrl' LI .anda Lpositiveegoing pulse will .be applied. via'zC zandzRI 8L to. thereonv trol grid offVzIZgsoithat the.firstngateicircuit-isr closed'. :and the .second opene'd.;

' These. operations lcontinue tand' itfiwill 'befiseerr that. thei control `valves VIIe-V15 .are rendered` eective .successively forz'equa-l 'durationsof;20 milliseconds Lunder the .controlfiof the triggerl'cirfcuits lf2-Vfl.; Whether ther-.control valvesii-confductor not', causing 'the' `transmissionio'f 'aspacerv or mark, depends on the absence. .or presence respectively of earth on the: corresponding. on of the leadsv I tozfinclusive.

Valves VI Il-VI'5"inclusive,y are fedfromiafcom mon anode resistor RI4'.andtheir common anode voltageis'therefore 4reduced whenany one ofthe valves isconducting. .The .common r'anode voltagev therefore follows faithfully the mark/space .siganais-as' determined by the 'pe'c'lrerl contacts; ilse; the voltage drops for 'a space andrises'for amark.

The common ano de voltage variation-developed across R`I`4l'is fed 'Via Va potentiometer RI 9; Rlto theflet-hand grid of"v`a`l`ve-`V8'. When thisvolt-v age fallsto 'the 'lowl (space) value, they common cathode voltage ofval've Vissuch as 'to ensure thatA the left-hand' triode is suppressed and-the right-hand 'triode conducts. v Y After 20 milliseconds the 'circuit changes over so-that the left-"handtriodeconducts andtheA right-hand issuppresse'd, provided that the coinmon anode voltage o'ffthe pulsing valves rises4 to the high (mark) value.'v 1

During the last 30 milliseconds vofa sweep none of the valves' VIIl-V'Ili willbe conductingand therefore 'the-'common' anode voltagey will be at the high (mark) value 'and the left-hand triode of valve V8 Vconducts to form'the stop signal;

The coil ofy output 'telegraph relay are connected "inthe anode circuits `of valvefV -in such Va manner that ywhen the 1`=:ft'l^iand` triode of the valve V81 conducts, the relay contacts'rest -in the mark position 'and when the righthand triode of the valve V8 conducts,` `the contacts rest in the space position Thusk the telegraph relay contacts transmitto line the 'start 'pulse,the ve unit code "pulses'and the stop pulse cfav 'telegraph'ch'aracter 'Ito' be transmitted.

At'the 'end ofv thesweep the common potential applied to the grids :of lthe lefth'andtriod'es of the trigger .circuits drops lto a.v minimum value and suppressesL th'esef triodes simultaneously; At "this instant positivezpulsesl 'are obtainedV from` each of i the kanod'es f ofN the left-hand .'.triodes of the 'triggerV circuits: Eachfiof these-positiver pulses is applieditozboth the fcorrespondingri'ghthand triode grid of the trigger circuitand in thescas'e of valves V3-V1 inclusive, is also appliedto the suppressor grid of th'e associated control.A valves VII-Vl5 inclusive. All the right-hand triodes of the trigger circuits therefore conduct at'the end of the sweep and in the case of'valvesV2-VS inclusive supply negative-going pulses'from their anodes to` the control"y grids of control valves VI |-VI5 inclusive.v Valvesf VI I-VI5 inclusive therefore receive two simultaneous pulses, a posi-1 tive-'going pulse on the 1 suppressor grid and a negative-going pulse on'the 'control grid, the latter of which predominates 'and holds thecontrol valve in the cut-off condition.. y f

A positive-goingv pulse from the Aright-hand anode of valve V'I is applied'tol the control grid of valve VIB at '120 milliseconds after the, start of the sweep. Valve VIIS is caused to conduct and in conducting to operate. the pulsing relay Contacts PI complete a circuit extending tothe autohead over the lead pand serves to step on the punched tape so that the next character is ready for transmission during the next: sweep of they time base. At the-end of the sweep when the'right-hand triode of valve V'II again conducts, the control grid of valve Vl'freceives a negativegoing pulse, thus suppressing fthe valve.

The alternative circuit'shown in Figs. 4 and 5 operates on a similar principle to that shown in Figs. -1l and 2, the differencev being that the control circuits include metal rectilers instead of pentode valves. In-the circuit shown in Figs. 4 and 5, the time base'generator consists of the double triode V2'I'While the cathode follower consists of the left-hand triode'of thedouble triode V278,- the right-hand triode correspondingito the pentode VIB of Fig. 2 which controls the stepping on of the punched tape. The output from thecathode follower is applied via R2I to the control grids ofthe left-hand triodes of valves V2I-V26 the cathode resistors R22, R23; R24, R25; R26, R21; R29, R29; R30, R3I and R32, R33 of which have differentv values as in the case of the previously described circuit. l

The trigger circuits consisting of valves V2 I-V26 operate in sequence with the rising out-'- put from the time base generator, the output Waveform being as shown in Fig. 3. It will be seen that at the instant when the left-hand triode of any trigger valve conducts, a positive pulse is obtained from the right-hand triode anode andas regards valves V22-V26 is applied to two control circuits which determine the -operation of the output valve V29. As regards valve V2I the positive pulse is applied to one control circuit and via a condenser to operate the-autohead drive circuit as will be described later.

Consider the condition of `the circuit at the beginning of a sweep. The ily-back at the end of the'previous sweep will cut off the left-hand triodes of all the trigger circuits and in particular the left-hand triode of V2I. 'I'his will cause a positive-going pulse to betransmitted from the leftehand anode via condenser C22 resistor R34 and rectifier MRZ'I to the right-hand control grid ofvalve'V29. When'the right-hand control grid of valve V29 receives the positive-going pulse, current flows through the right-hand triode and lower coil of telegraph relay TI causing a space signal to be transmitted to line.` After 20 milliseconds of the sweep. the left-hand triode, of valve V22 conducts` and the right-hand triode 6: is suppressed. The positive-going pulse from the right-hand anode'is fed via condenser` C24 re` sistor R36,;rectifler MR25 and commonffcon'trolwire 20 to the left-hand control grid of valve V29. If the pecker contacts associated with leadv I are in the spacing condition, lead I will be 'disconnected,A and the positive-going pulse `from righthand triode anode of valve V22 via condenser- C25, resistor R31 and rectifier MR26 will be al.- lowed to pass to the common control wire 2| and to the right-hand control grid of valve V29. Valve V29 now receives simultaneous positivegoing pulses on both control grids. 'I'he right-` hand control grid of valve V29 has a time constant circuit composed of condenser C21and' resister R40. Similarly the -left-hand controlgrid of valve V29 has condenser C26 resistors E38-and R39. Condenser C21 andv resistor vR40 has a longer time delay than that of condenser C28 `and resistors R38 and R39. Consequently, ofthe two positive pulses simultaneously applied to the control grids of valve V29, that of the right-hand control grid will persist longer andcause the right-hand triode of valve V29to conduct. Current flows through the lower coil of 4telegraph relay TI and causes a spacing signal tobe sent to line. If, however the pecker contacts arev in the marking condition an earth is applied over lead I to prevent the positive pulse from `right-- hand anode of valve V22 being applied to the right-hand control grid of valve V29. Thus the left-hand triode of valve V29 conducts, current passes through the upper-coil of telegraph relay TI and a marking signal is applied to line. After a further 2() milliseconds i. e.40 milliseconds after the beginning of the sweep valve V23 will be triggered by the sweep voltage and positive-going pulse will be applied to the common control wires as in the case of valve V22.

These operations continue and whether y the telegraph relay TI transmits marks or space de -f pends on the presence or absence respectively of earthen the corresponding one of the leads'I to 5 inclusive in thesame way as for the circuit of Figs. 1 and 2. i

At the end of milliseconds from'fthe begin--v ning of the sweep, valve V2I will be triggered by the sweep voltage. The right-hand triode anode of valve V2I will deliver a positive-going pulse via C23, R35 and MRM to the common control Wire 20 associated with the left-hand controlgrid of valve V29, ConsequentlyV a marking signal will be transmitted by the telegraph relay TI, this constituting the stop element.

At the end of the sweep the common potential.

applied to the grids of the left-hand triodes of the trigger circuits drops to a minimum value and suppressed these triodes simultaneously.l The right-hand triodes ofthe trigger circuits will de.- liver negative-going pulses towards .the common control wires but the rectiilers MR22` and'MR23 present an eiective shunt path to these pulses. In the case ofvalve V2Ihowever, a positive-v going pulse is delivered from the left-hand triode anode which passes to the right-hand control grid of valve V29 and causes a spacing signal to be transmitted by telegraph relay l'I'Iythus constituting the space element of anew-character.

A positive-goingv pulse from thei right-hand anode of valve VZI is also applied via condensei C2I and lead 22 to the control grid ofthe right-fv hand triode of valve V28 at 120 milliseconds after the start of thesweep. The right-hand vtriode of V28 is caused to conduct and in conducting to operate the pulsing relay P with resultsl as previmounted remote "from the traffic oice to facilitate.engineering-supervision. f y

Small electro-magnetically steppedauto-heads in fthe 'trame oiilce may be Varranged to'feed into therelectronic distributor which maybe Amol'inted infanyconvenient position. f More accuratetimingof elements and greater stability of 'speed 'are obtained by means of Al,the invention. Y Y l 'Byfmakingthef'cathoderesistors of each ofthe triggervalvesvariable, 4the length of any individualtelegraph character elementcan be altered atwillthus'f'providing a simple means of 4producingartiiicial distortionfor testpurposes,

I-claim: l

Inatelegraph distributor, a transn'iitting relay, apl'urality of Acontrol circuits for controlling the operation of ,said transmitting relay and each-including a thermionic tu'be having at least acathode, a vcontrolgrid, a screen grid, a suppressor grid and an anode, a plurality .of leads forsimultanecusly applying to the screengrids ofsaid' thermionictubes .oneof two distinctive potentials depending on the elements .of the messagesignal to be transmitted, a .pluralityv of trigger circuits, means generating a AsaWtooth triggering'.vvaveforniV for application in common tosaid triggering circuits, means for biasing said 'trigger circuits to cause the successive operation ofsaidztrigger circuits in response tothe .common application thereto of said sawtooth triggeringtvaveform, means responsive to the ,operationof each trigger circuit for transmittinga pulseto the control grid .of the tube' in 'the associated control circuit, the thermionic'tube'in each of said control `circuitsinresponse to said pulse of one polarity'transmitted tothe control grid'thereof andin response to one .distinctive potential 'applied tothe .screen grid over the associated yone of said leads being rendered. conductive to cause ,said transmittingrelay to transmit a marking signal andbeing. maintained nonconductive in response lto said pulse of .one polarity transmitted to the control grid thereof andin response to the other ,distinctiveypotential appliedto the screen grid over the .associated Y one ofsaid leads to ,causesaid ytransmitting relay to transmit a spacing signal. 2. A telegraph distributor asclaimed in claim 1 wherein meansare provided which in response tothe operation of any .trigger circuit serve vto transmit a pulse' tothe suppressorgrid ofthe tubevv inthe previously operated control circuit tocut 01T said-tube.

`3."In la telegraph distributor, a transmitting relayya' plurality of control circuits for controlling'theoperation of said transmitting relay and each 'including a kthermionic vtube `having "at leastthree control electrodes, a plurality of Vleads fori'simultaneous'ly applying to a iirst control electrode of v*said-tubes distinctive potentials-'depending -on the elementsr of the message rsignal to be transmitted, a plurality `of :trigger Y circuits, means l:for -Lxsucces'sively operating @said ltrigger' 8. circuits.:A an -..A.f.:C. :connection 'ibetween-"a-.ssecond control :electrode lsofthe :tubes in said .control circuitsand the :associatedone of :said :trigger circuits zand'betweeni-a .third control electrode of :the tubes-"in said. `:control circuits :and 'the trigger c Acircuit operated next .after :said .associated'ztrigger lcircuitI `whereby :on the 'operation of Yone of Tsaid :triggercircuitsa pulse of :one polarityy is transmitted ,to the Tsecond .control electrode of "the :tube .fin-:..the associated control circuit while .on 4:the .operation :o'f vthe i'trigger circuit 'nexti after '.fsaid trigger i circuit 'a pulsev of opposite polarityiis transmitted-'to' the .third control electrode of saidtubanthesaid-tubein-:respouse :tofsaid pulse` of f one; polarity y=and in response to fone distinctive 'potential .-applied'to.

saidrst .control electrode-over the associated onev o'f f said `leads bei-ng .rendered :conducting :to cause said 'transmitting #relay v:to "transmit fa marking signal and to be rendered non-conducting in response to said pulse of opposite polarity While being maintained non-conducting in response to said .pulse of` one polarity and in. response to. .another 1. distinctive potential .to .cause said transmitting relay to Vtransmit a .spacing signal.

.4; A ltelegraph distributor `as .claimed inclaim 3 .comprisinga lcommon anode Vload for said tubesiand meansf-Vforapplying the voltage varia-v tions acrosssaidfanode loadto an operating. oircuit .for said transmitting relay.

:5. A telegraph distributor as claimed in claim 4 wherein :said operatingcircuit comprises .two thermionictubes having at least three electrodes and a Vcommon vcathode .resistor and .said transmitting relay has two 4,windings one. in the anode circuit of -each tube,.the control grid and cathode of. oneoffsaid tubes being connected toaxed potential-and. ,theanode ofthe second 'tube while the voltage variations r`acrossxsaid anode ,load are yapplied tothe control grid .of said second tube. y

6. 5A telegraph distributor as Vclaimed in claim 3 comprising means `for generating .a linearly .Varying waveformior .application to the trigger circuits lto .cause the successive operation thereof, a further trigger circuit and associated control circuit and means .for rendering the thermionic tube insaidassociated control circuit conducting atthe` instant Vwhen Vsaid Waveform Vcommences tol cause said transmitting -relay to transmit a start.v signal, lsaidtrigger circuit being the iirst to be operatedfand in operating .to render said tube non-conducting v-to terminate said start signal. 7. lAl-telegraph fdistributorfasclaimed .in claim 3 wherein the control circuit associated with the last'trigger :circuit to be operated .includes fa thermionicy tube and :an electromagnetic .relay is includedrin the anode circuit of said tube to disconnectfthe :distinctive potentials representative of one message rcharacter Vfrom said leads and 'to connect further distinctive potentialsv thereto'/representative .of the'nextfmessage character-to: be transmitted.

:Inra telegraph f'distribu'tor, 'a ltransmitting relay, ,a plurality `'o'f'jcontro'l circuits;V a rst common control lead for fsaid ncontrolcircuits, aiseeond common control. flead for said :control circuits, a-plurality offurther'lea'ds for simultaneously. applying to'saidcontrol .circuits distinctive potentials dependingxon thezelements :of themessage characterv signal: toibe: transmitted, Yan operating. circuit for. said transmitting relay 'to` which said'commo'n control lleadsare connected, a plu-fr tive potential is applied to said further leads andv means in said operating circuit for causing said transmitting relay to transmit a marking signal in response to pulses transmitted thereto over said first common control lead and to transmit a spacing signal in response to pulses transmitted thereto over said first and second common control leads;

9. A telegraph distributor as claimed in claim 8 wherein said control circuits comprise two resistance/condenser combinations connected individually to said first and second common control leads and in parallel to the output of the corresponding trigger circuit, said further leads being connected to a point in the resistance/ condenser combination connected to said second common lead to enable the pulses received from the corresponding trigger circuit to be shortcircuited.

10. A telegraph distributor as claimed in claim 9 wherein said resistance/condenser combinations include a rectier to ensure that pulses of one polarity only are transmitted to the Operat ing circuit for said transmitting relay.

11. A telegraph distributor as claimed in claim 8 including a further trigger circuit and control circuit, means for generating a linearly Yvarying recurrent waveform and for applying said Waveform simultaneously to said trigger circuits to eilect their successive operation, said trigger circuits being returned to normal at the end of said waveform whereupon said further trigger circuit transmits a pulse through said control circuit to the second of saidcommon control leads to cause said transmitting relay to transmit a start signal while the operation of said further trigger circuit transmits a pulse through said control circuit to the rst of said common control leads to cause said transmitting relay to transmit a stop signal.

12. A telegraph distributor as claimed in claim 11 including a third control lead extending from said further trigger circuit, an electromagnetic relay and means responsive to the transmission of a pulse over said third lead on the operation of said further trigger circuit for operating said relay to disconnect the distinctive potentials representative of one message character from said further leads and to connect further distinctive potentials thereto representative of the next message character to be transmitted.

13. A telegraph distributor as claimed in claim 8 wherein the operating circuit for said transmitting relay comprises a relaxation circuit including two thermionic tubes, each having at least a cathode, a control grid and an anode said iirst common control lead being connected to the controlgrid of one of said tubes while said second common control lead is connected to the control grid of the other of said tubes, the time constants of the control grid circuit of said one tube being less than that of the control grid circuit of said other tube whereby if simultaneous pulses are transmitted over both common control leads that transmitted over the second control lead is effective.

14. In a telegraph distributor, a transmitting relay, a plurality of trigger circuits 'each comprising two thermionic, tubes having a cathode a control grid and an anode, a common cathode resistor for said tubes, an A. C. connection from the anode of one of said tubes to the control grid of the other and to the common cathode resistor. means for generating a sawtooth triggering waveform for application in common to said trigger circuits, the values of said cathode resistor being different for eachv trigger circuit whereby the common application of said sawtooth triggering waveform to said trigger circuits causes said trigger circuits to operate successively, a plurality of control circuits each individual to one of said trigger circuits and each connected to a lead to whichl one of two distinctive potentials is applied depending on the kind of element of the message character to be transmitted, means responsive to the operation of a trigger circuit for transmitting a pulse to the associated control circuit and means in said control circuit responsive to said pulse and to one distinctive potential applied to the associated lead for causing -current to flow through said transmitting relay to transmit a marking signal and responsive to said pulse and the other distinctive potential applied to the associated lead for causing current to iiow through said transmitting relay to transmit a spacing signal. y

15. In a telegraph distributor, a transmittin relay, a plurality of trigger circuits, means for generating a sawtooth triggering waveform comprising an asymmetric multivibrator and a cathode follower output circuit, means 'connecting said cathode follower output circuit in parallel to` said trigger circuits, means for biasing said trigger circuits differently to cause the successive operation of said trigger circuits in response to the common application thereto of said sawtooth triggering waveform, a pluralityl of control circuits each individual'to one of said trigger circuits and each connected to a lead Ato which one of two distinctive potentials is applied depending on the kind of element of the message character to be transmitted, means responsive to the operation of a trigger circuit for transmitting a pulse to the associated control circuit and means in said control circuit rei sponsive to said pulse and to one distinctive potential applied to the associated lead for causing current to flow through said transmitting relay to transmitav marking `signal andv responsive to said pulse and to the other dis tinctive potential applied to the associated lead for causing current to flow through said transmitting relay to transmit a spacing signal.

GORDON TAYLOR DAIN.

REFERENCES Orrin) le of this patent:

UNITED STATES PATENTS Number Name Date 1,801,657 Buyko Apr. 2'1, 1931 1,823,739 Horton Sept. 15, 1931 2,210,574 Fitch Aug. 6, 1940 2,265,216 Wolf Dec. 9, 1941 2,457,819 Hoeppner Jan. 4, 1949 2,468,462 Rea Apr. 26, 1949 l FOREIGN PATENTS Number Country Date Great Britain Nov.v 22, 1948 

